The present invention relates to a valve arrangement for carrying over low pressure gases from a pressure container filled with high pressure gas to a consumer device.
A valve arrangement of the type under discussion has been disclosed, for example in EP No. 00 54 717. This arrangement has been utilized in households for drink automates for producing carbon-acid-containing drinks.
In the valve arrangement of the conventional type, a pressure-reducing valve is inserted immediately in a pressure container attachment simultaneously with a valve member. The pressure-reducing valve includes a piston-shaped closing member which slides in a bore of the valve member. The closing member at the side of the pressure container is loaded with a valve spring which is supported on the bottom of the valve member bore. An opening plunger is screwed in the closing member at the other side. The opening plunger is displaceable relative to the bolt forming a valve seat, the screw being threaded in the valve member. The conical end portion of the plunger extends in the closed position over the end face of that screw.
The pressure-regulating valve is formed as a diaphragm. The diaphragm forms a structural component of the two-part housing in which a lower pressure safety valve and a check valve are arranged radially opposite to each other. The housing of the pressure regulating valve can be plugged into the pressure container attachment. At the side of the pressure reducing valve, facing the opening plunger, an opening projection, extended in the axial direction of that plunger, is provided. That projection is connected with the diaphragm and follows the movements of the same.
A disadvantage of the above described conventional valve arrangement resides in that the pressure-reulating spring of the pressure-regulating valve must have a comparatively small diameter. Namely, the diameter of the spring disc lying inside the diaphragm is limited and therefore the diameter of the freely movable portion of the diaphragm does not exceed a non-realistic value. The small diameter of the spring leads, however, to a relatively large spring constant, whereby adjustability of the diaphragm-type pressure regulator is limited. This situation is further unfavorably affected by the fact that with a longer careless use of the valve arrangement the spring constant will change anyhow. Furthermore, the material of the diaphragm is very absorptive for CO.sub.2. Consequently, it should be taken into consideration that depending on the time of action of CO.sub.2 on the diaphragm the latter would swell and become thicker which would also eventually cause change in adjustability of the diaphragm.
A further disadvantage of the known valve arrangement is that the pressure-reducing valve receiving gas at high pressure from the pressure container requires a large gripping surface. Thus, in order to open the pressure-reducing valve a considerable force is required. The opening force must be even greater when the gas pressure increases due to temperature increase. It should be noted that the conventional valve arrangement is used in the temperature range at most between 15.degree. C. and 40.degree. C. and pressure in the pressure container at this temperature range can vary between about 40 and 140 bar. Due to this dependence of gas pressure upon temperatures the preciseness of the device during the cooperation of the pressure regulating valve with the opening plunger is reduced the stronger are fluctuations in temperatures at the location of the valve arrangement. The known valve arrangement functions well only when the temperature at its location is known and this temperature remains constant so that the pressure-regulating valve can be adjusted to this temperature.